Sugar evolved as an incentive to get things to eat fruit, which contain seeds, allowing seed dispersal.

@rg255 this might be the evolution of the fruits, but it doesn't explain why we had evolve to like it. And in that case, what happened first?

Who said fat doesn't taste better than sugar? Add butter in almost anything and it becomes so much better. IMO, the question is opinion-based. Some people are more attracted into fats and some others are more attracted toward sugar. You might want to study a little bit on the role of fats in gastronomy.

@Remi.b I dare you to eat 300 grams of lard.

@MatasVaitkevicius I dare you to eat 300 grams of sugar.

@Remi.b Ok have you seen children eating lard candy? Not chocolate just pure fat...

@Remi.b Maybe because it doesn't taste very nice, lol

Have you seen a good cook making meal without fats but only sugar? No, because that would be pretty awful. I still think your question is a matter of opinion. I personally eat very little sugar but a good deal of fats (french food culture).

@Remi.b you are talking about additives used with lard, and twisting the question, we are talking about pure lard.... Pure fat vs pure sugar

I would personally prefer eating pure lard (or other source of saturated fat, I am not sure why you talk about lard specifically) than pure sugar. A good slow baked lard is amazing (whether accompanied or not). I am actually putting lard in a vegetable soup tonight (it's already on the fire :D) But anyway, we might not go very far with our current conversation. I'll let the others comment on that matter further as I seem to fail to communicate to you why IMO the question is opinion-based.

@Remi.b Remi how much do you weight? Fact stands there is pure sugar candy but there is no pure fat one....

I am pretty slim. I could have taken your question as a bit of an offense, esp. if I were complexed about my weight. Be careful! But anyway.... this is really not the point of the discussion. Fact stands there is pure lard in sauerkraut but not pure sugar in sauerkraut (when prepared with good ingredients).... and I love sauerkraut. Have a good day!

Offer a child a choice between a box of sugar cubes and a giant bag of fruit flavored gummy candies, and almost all will take the fruit flavored gummy candies. Evolutionary pressure has left us with a taste for fruit, not a taste for pure sugar. Refined sugar and lard are relatively recent inventions that weren't part of the environment humans evolved in. People do find fat quite tasty though. Particularly in arctic cultures blubber and marrow are highly prized.

@Remi.b I just wanted to make sure this isn't one of those cases where people obsessively eat fat foods and drink oil when getting gastric rings in their stomach...

No, I eat quite healthily and almost never eat fast food (once or twice a year only). But if anyone with a gastric ring is reading what you are writing, (s)he can be very offended and we don't want that on SE sites. Plus, the question was not relevant to the main point of the discussion. Your comment should be flagged as being offensive. Of course, I understand you did not mean to offend anyone.

@CharlesE.Grant The discussion of pure fat vs pure sugar doesn't make any sense in an evolutionary context. Neither food was available in 'pure' form long enough to allow evolution to adapt to it. Evolution adapted to sugar and fat mixed with other stuff.

@Nicolai pure sugar is sweet....

@MatasVaitkevicius sure it is, but you still can't compare it to pure fat, because pure fat has a different taste, than fat with other food.

@Nicolai why can I not compare pure fat with pure carbodidrate? I know fat has different taste and it tastes not as good as sugar does, and hence the question... if fat = 9 cal per gram and carb = 4 why then sugar tastes better than lard (pure carb vs 99% pure fat)....

@MatasVaitkevicius Sugars can directly be tasted, Fat can not - therefore pure sugar tastes good, while fat does not. Since pure fat was never available during evolution, it didn't give any advantage to 'taste' it. Pure sugar on the other hand has the same taste as sugar in fruits, or dissolvedbroken up carbohydrates - which were availabe during evolution.

@Nicolai It sounds like you have a good answer to this question, and your comments also clarify why it is a reasonable question. Perhaps it should still be reworded a bit, I but I am voting to reopen it so it can be answered.

@Nicolai isn't that the heart of OP's question though? Is there a chemical reason why sugars can be directly tasted but fat cannot? If not, then that does raise the question of why we evolved to taste sugar and find that taste generally appealing, but did not evolve to similarly taste fat. (edit: it's true that the rest of Nicolai's answer does offer a possible answer to that)

@RozennKeribin I don't think there is any reason to assume that (bio)chemically it is harder to taste fat in contrast to sugar - proving this is probably tricky though. Thinking about evolutionary reasons for this is possible, but always a bit speculative ^^ Also see here, that there may possibly be a taste receptor for fat - so its definitely possible.

Talking about pure carbohydrate, what taste do you get when you eat some starch? Most probably nothing, because it does not dissolve in saliva (it does become sweet though, due to amylase). We could apply same thing to fats. Also, sugars are sweet so that people eat more and more of it, but since fat contains so high energy content, it might be better to not get any taste for it (also keeping in mind how hazardous fats are for body). If this seems plausible, I would like to add it as an answer.

@another'Homosapien' Yeah but in the old days when we were controlled by instincts mostly, sweet meant = eat a lot... but eating a lot of fats in the old days would be a better strategy for survival as food was scarce back then... So if sugar tastes sweet fat should give you euphoria as it is 2.25 times higher in calorie content... but it doesn't... hence the question...

You didn't pay attention to a crucial point in my comment, we can only evolve to things which are possible. We can't make a hydrophobic saliva just so that fats dissolve in it. Maybe we always used to get enough fat for survival, so there was no need to make it sweet.